1. Field of the Invention
The present invention is directed to an improved construction device, and specifically an improved hold-down device for building construction applications.
2. Description of the Related Art
Nature's elements exert extreme forces on building walls and elements. High winds and earthquakes, in particular, cause forces that place considerable strain on the stability of a building. Proper distribution of these forces is critical to ensure the stability of a structure. At the core of building stability is the building's foundation and thus securing the walls of a building to the foundation greatly improves structural performance.
Structures known as “hold-downs” are used to transfer tension loads between floors, to tie purlins to masonry or concrete, and in other applications. The loads may then be resolved in the foundation, where they appear as tension and compression forces.
Buildings are often composed of long walls, (walls with a length greater than the height) and short walls (walls that have a length shorter than the height). The tendency for a wall to lift vertically off a foundation is inversely proportional to the length of the wall. Tall narrow shear walls, which may be found in nearly all homes, act as lever arms or cantilevers, and magnify imposed loads. Horizontal loads are magnified when resolved into vertical components. In certain instances, the actual load on the support system may be magnified to several times the originally imposed load.
There are a number of sources of deflection at hold-down connections. For example, bolt slip can occur at hold-down stud bolts. When a hold-down is installed on only one side of the stud, an eccentricity exists during loading which can cause more movement in the wall system. Wood at the end of the studs (sill plates, rim joists, etc.) may crush under normal dead and live loading; additional compressive forces due to overturning during earthquake and high wind loads add to the deflection. Other sources of deflection exist and the foregoing is illustrative only.
Hold-downs are therefore required to resist a substantial amount of force to be effective. In addition, hold-downs need to be easy to install and inexpensive to fabricate. Accordingly, a need exists for a balanced hold-down that may be easily installed.